Excerpt from IEEE specifications:
For an implementation that supports version A of the protocol, a received EAPOL PDU of a given Packet Type that carries a protocol version number B is interpreted as follows:
d) Where B is greater than or equal to A, the EAPOL PDU shall be interpreted as if it carried the
supported version number, A. Specifically:
1) All EAPOL PDU parameters that are defined in version A shall be interpreted in the manner
specified for version A of the protocol for the given EAPOL PDU Packet Type.
2) All EAPOL PDU parameters that are undefined in version A for the given EAPOL PDU Packet
Type shall be ignored.
3) All octets that appear in the EAPOL PDU beyond the largest numbered octet defined for
version A for the given EAPOL PDU Packet Type shall be ignored.
As a consequence of the rules stated in d) and its sub-bullets, a version 1 implementation must reply to a v3 Request as it would be a v1 PDU.